Four days after the bodies of Hannah Witheridge, 23, and David Miller, 24, were found with severe head wounds on a beach on Koh Tao, police admitted forensic evidence had ruled out all of their suspects.
Post-mortem examinations revealed Miss Witheridge, from Norfolk, died from head wounds while Mr Miller, from Jersey, died from severe blows to the head and drowning. A bloodstained garden hoe, believed to be the murder weapon, was found nearby.
Two British brothers who were being questioned by police have been told they are free to return home, it was reported.
And Burmese migrants on the island of Koh Tao who were arrested after bloodstains were found on their clothes have also been eliminated from inquiries after no matches were found between them and DNA found on Miss Witheridge and a cigarette butt at the scene.
DNA results also indicated that semen discovered on Miss Witheridge’s semi-naked body was not from Mr Miller, according to reports.
Royal Thai Police had previously insisted they had found “strong evidence” in connection with the deaths.
They have said they are now looking for three westerners who were seen playing a guitar near the scene, on Koh Tao’s main Sairee beach.
Police colonel Prathum Reungthong said: “They were singing western songs and a guitar was being played. We believe there were three people singing in the dark but they may have seen something or know something which could be vital. We are working hard at trying to find those who are in the singing group. We don’t know if they are still on the island.”
The family of Miss Witheridge earlier had an emotional meeting with Thailand’s deputy police chief, in which they were given updates on the investigation. British consul Michael Hancock said: “It was very important for the family of Hannah to be able to speak directly with someone leading the investigation and to hear information directly from the police.
“The family are deeply distressed at this time and my role is to support them at this very, very difficult time, and obtaining information directly and very helpfully from the police has been good for them.”
Thailand’s military ruler also apologised yesterday for suggesting foreign visitors to his country’s world-famous beaches might be unsafe wearing bikinis.
In the face of mounting criticism, General Prayuth Chan-ocha said: “I apologise that I have spoken too harshly.
‘‘I didn’t mean to criticise or look down on anyone. I can guarantee that Thailand is still safe. I wanted to warn the tourists to be careful.”
Earlier this week, he claimed foreigners visiting the south-east Asian country think “they can do whatever they want, wear bikinis wherever they like, but will they be safe?”
And he was quoted as saying: “Can they be safe in bikinis unless they are not beautiful?”